DESCRIPTION

The
nearbyint(),
nearbyintf(),
and
nearbyintl()
functions round their argument to an integer value in floating-point
format, using the current rounding direction (see
fesetround(3))
and without raising the
inexact
exception.
When the current rounding direction is to nearest, these
functions round halfway cases to the even integer in accordance with
IEEE-754.

The
rint(),
rintf(),
and
rintl()
functions do the same, but will raise the
inexact
exception
(FE_INEXACT,
checkable via
fetestexcept(3))
when the result differs in value from the argument.

RETURN VALUE

These functions return the rounded integer value.

If
x
is integral, +0, -0, NaN, or infinite,
x
itself is returned.

ERRORS

No errors occur.
POSIX.1-2001 documents a range error for overflows, but see NOTES.

ATTRIBUTES

For an explanation of the terms used in this section, see
attributes(7).

Interface

Attribute

Value

nearbyint(),
nearbyintf(),
nearbyintl(),
rint(),
rintf(),
rintl()

Thread safety

MT-Safe

CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.

NOTES

SUSv2 and POSIX.1-2001 contain text about overflow (which might set
errno
to
ERANGE,
or raise an
FE_OVERFLOW
exception).
In practice, the result cannot overflow on any current machine,
so this error-handling stuff is just nonsense.
(More precisely, overflow can happen only when the maximum value
of the exponent is smaller than the number of mantissa bits.
For the IEEE-754 standard 32-bit and 64-bit floating-point numbers
the maximum value of the exponent is 128 (respectively, 1024),
and the number of mantissa bits is 24 (respectively, 53).)

If you want to store the rounded value in an integer type,
you probably want to use one of the functions described in
lrint(3)
instead.

SEE ALSO

COLOPHON

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